The present invention relates to a brake signal transmitter with integrated addition redundancy.
A brake signal transmitter of conventional design is disclosed, for example, in German patent DE-A1-33 08 279, in which it is termed a xe2x80x9cmotor vehicle brake valve.xe2x80x9d
The disclosed brake valve is designed to primarily effect electrical braking in a towing vehicle. For this purpose, a magnetoresistive displacement transmitter is provided, which emits a measuring signal for an electrically controlled brake, i.e. the operating brake of the vehicle. Such signal is dependent upon the actuation of a pedal plate. When the pedal plate is actuated, a braking pressure is also initiated in a pneumatic circuit. The braking pressure within such pneumatic circuit acts upon the brake cylinder preferably only in the event of failure of the electrical circuit. The pneumatic circuit thus represents a redundancy in addition to the electrical circuit.
A mechanically functioning apparatus for the production of a first pneumatic braking pressure component which acts preferably as a redundancy pressure, and an apparatus for the production of an electrical measuring signal for a second, electrical, braking component which is put into effect by priority, is taught in the literature.
A braking pressure modulator consisting of a two-circuit triggered relay valve system and a magnetically actuated valve system is disclosed, for example, in European patent EP-B1-0 447 750 (corresponding to U.S. Pat. No. 5,294,190 which is incorporated herein by reference). The relay valve system employed therein is of accumulating design normally available on the market. Used in such context, the term xe2x80x9caccumulatingxe2x80x9d means that the two control devices of the relay valve system produce a higher pressure at their outputs when subjected to pressure at the same time than when only one of the control devices is subjected to pressure.
The magnetically actuated valve system is designed so that it emits a pressure which is determined as a function of the supplied magnetic current strength. The two-circuit triggered relay valve system (identified by reference numeral 44 in FIG. 4 of European patent EP-B1-0 447750) is controlled by the pressure produced by the magnetically actuated valve system (reference numeral 40 in FIG. 4 of EP-B 1-0 447 750), as well as by a mechanical braking pressure system (reference numeral 5 in FIG. 4 of EP-B1-0 447 750). The pressure produced by the two-circuit triggered relay valve system represents the braking pressure. The two-circuit triggered valve system thus adds the influences of the pressure appearing at its two inputs by producing a braking pressure augmented by a quantity of air, the level of which depends on the sum of the two input pressures. Such valve system therefore contains an addition element for the formation of the sum.
Relay valves of conventional form generally include a relay piston, the piston surface of which serves as the active surface for a pre-pressure applied to a pneumatic control input thereof. The excursion of the relay piston actuates an air admission and venting valve in such manner that the end position of both valves is attained when the generated pressure has become equal to the pre-pressure.
Two control inputs are provided for a two-circuit triggered relay valve, and each pre-pressure applied to these control inputs acts upon the relay piston via an active surface. Assuming identical active surfaces for both control inputs, it is essential that a force be applied to the relay piston which is equal to the sum of these two pre-pressures. The relay piston therefore constitutes the addition element. The addition is effected by an equilibrium which is established on the relay piston between the force of the generated pressure exerted upon the relay piston and the forces exerted upon it through the two pre-pressures.
The two pressures appearing at the two inputs of the two-circuit triggered relay valve system (identified by reference numerals 42, 43 in FIG. 4 of European patent EP-B1-0 447 750) thus represent the pre-pressures to be added. The corresponding pneumatic circuits of the units producing these pressures (reference numerals 40, 5 in FIG. 4 of EP-B1-0 447 750) serve for the transmission of air, the pneumatic pressure thereby assuming, in this instance, the function of a force transmission.
European patent EP-B1-0 447 750 furthermore discloses a brake signal transmitter located upstream of the braking pressure modulator for control thereof, the braking pressure modulator transmitting an electric actuating signal dependant upon the actuating force, or the actuation displacement, produced by the driver""s foot acting upon an electric element of the brake signal transmitter, to the magnetically actuated valve system. At the same time, the brake signal transmitter controls the level of the redundant braking pressure from a pressure supply as a function of the braking pressure control system on the pressure part thereof representing the above-mentioned mechanical braking pressure control system.
The braking pressure emitted by the braking pressure modulator thus consists of the redundant braking pressure and a braking pressure component based on the magnetic actuation. It is a feature of European patent EP-B1-0 447 750 that the force of the magnetic current is adjusted such that the braking pressure component based on the magnetic actuation precisely amounts to the difference between the braking pressure requirement corresponding to the driver command and the braking pressure component based on the redundant braking pressure.
In order to reliably utilize the principle of the addition redundancy according to European patent EP-B1-0 447 750, it is necessary to provide a plurality of different components around the brake signal transmitter (identified by reference numerals 5, 6, 7 in FIG. 4 of EP-B1-0 447 750). A further disadvantage of the invention disclosed in EP-B1-0 447 750 is that, as described, pneumatic connections must be provided which serve merely for the force transmission to those devices which carry out the adding function. This applies particularly to the pneumatic connection which transmits the redundancy pressure produced in the brake signal transmitter based on the driver actuation to the adding device, which is provided in the form of a two-circuit triggered relay valve system (identified by the reference numerals 5 after 9 in FIG. 4 of EP-B1-0 447 750).
It is therefore the object of the present invention to provide a brake signal transmitter of the above-mentioned type which contains the controlling functions for the addition redundancy.
It is a primary object of the present invention to ensure that the pneumatic connections which are conventionally provided solely for the force transmission of a force component derived from the force of the foot acting on the brake pedal, or from the range covered by the brake pedal when acted upon to a device carrying out the addition, are no longer needed.
In accordance with these and other objects of the invention, there is provided a brake signal transmitter for a braking system installed in a vehicle which includes a vehicle control system. The brake signal transmitter includes an actuating device for actuation of the brake signal transmitter by the driver and a sensor device for detecting driver actuation of the actuating device. The sensor includes an output connected to an input of the vehicle control system. The brake signal transmitter further includes a pressure-producing device for producing a braking pressure in response to the driver actuation. Such pressure-producing device includes an input for a first physical magnitude derived from the driver actuation. The pressure-producing device further includes an additional input for a second physical magnitude derived from an output of the vehicle control system.
By virtue of the attendant simplification of the pneumatic system, components, such as pressure-controlling valve systems, can also be dispensed with. In addition to cost reduction, the omission of components also provides the advantage that reliability of operation is increased.
The invention provides the additional advantage that building space and weight are saved. The savings in building space allows the brake signal transmitter to advantageously be integrated, together with its peripheral components, into a pedal box which is produced in advance as a prefabricated system support in the vehicle.
In a further development of the invention, limitations resulting from the planning of force-range in order to achieve a desired xe2x80x9cpedal feelingxe2x80x9d while maintaining presently constant operating capability of the combination brake signal transmitter/pedal are obviated. In this regard, the invention offers the advantage that this operating capability is variable, and that the needs of a particular user can therefore be met, to a great extent, in the design phase.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements, and in which pneumatic connections are depicted in the form of continuous lines, and electrical connections in the form of broken lines.